Concept:
This reaction involves two important organic transformations:
• Protection of amine group (acetylation)
• Friedel–Crafts acylation (electrophilic aromatic substitution)
Step 1: Acetylation of Aniline
\[
C_6H_5NH_2 + (CH_3CO)_2O \rightarrow C_6H_5NHCOCH_3
\]
• The –NH$_2$ group is highly activating and can lead to side reactions
• Hence it is protected as –NHCOCH$_3$ (acetanilide) • This reduces its reactivity and avoids complex formation with AlCl$_3$
Important: • –NHCOCH$_3$ is still an ortho/para directing group • Para position is favored due to less steric hindrance
Step 2: Friedel–Crafts Acylation
Reagent:
\[
\text{ClCH}_2\text{COCl} / AlCl_3
\]
• Generates electrophile: \(\text{ClCH}_2CO^+\)
• This electrophile attacks aromatic ring
Orientation: • –NHCOCH$_3$ directs substitution to ortho and para positions
• Para product dominates due to steric factors
Final Product Formation: • Acyl group (–COCH$_2$Cl) attaches at para position
• Amide group remains intact
Thus structure corresponds to option (A)
Why other options are incorrect: • (B) Incorrect positioning wrong substitution
• (C), (D), (E) show either:
• Unprotected amine (not possible under AlCl$_3$)
• Wrong directing behavior
• Multiple substitutions inconsistent with mechanism
Conclusion:
\[
\text{Major product is para-substituted acetanilide derivative}
\]
